linux-kernel - Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

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Message-ID: <aOY_1KhqJO2opqk2@kuha.fi.intel.com>
Date: Wed, 8 Oct 2025 13:41:24 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Konrad Dybcio <konradybcio@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Benson Leung <bleung@...omium.org>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	Andrei Kuchynski <akuchynski@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Guenter Roeck <groeck@...omium.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter
 type bitfield values

On Fri, Sep 26, 2025 at 02:32:57PM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> 
> The value has been amended with the release of the USB Type-C
> Specification v2.1, reportedly as an erratum.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

Makes sense to me. FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> I bundled a change to the CrOS EC driver based on the assumption that
> it worked around the faulty definition. I see the Intel PMC mux driver
> also checks for this bit, but it seems like that driver assumes that
> the value is in-spec (i.e. it may be buggy as of right now).
> 
> Adding the respective maintainers to make sure everyone can see this.
> ---
>  drivers/platform/chrome/cros_ec_typec.c | 2 +-
>  include/linux/usb/typec_tbt.h           | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index b712bcff6fb2674ec79286159090df6d79b32e9a..d80f3de1b87c362a2825bd19f826c5be077583aa 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -585,7 +585,7 @@ static int cros_typec_enable_tbt(struct cros_typec_data *typec,
>  	data.device_mode = TBT_MODE;
>  
>  	if (pd_ctrl->control_flags & USB_PD_CTRL_TBT_LEGACY_ADAPTER)
> -		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_TBT3);
> +		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_LEGACY);
>  
>  	/* Cable Discover Mode VDO */
>  	data.cable_mode = TBT_MODE;
> diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
> index 55dcea12082c80defeb6f199ad333279b58adcd7..6bf208c9dd5037f162678bc0be5be7ae1ca0deca 100644
> --- a/include/linux/usb/typec_tbt.h
> +++ b/include/linux/usb/typec_tbt.h
> @@ -27,8 +27,8 @@ struct typec_thunderbolt_data {
>  /* TBT3 Device Discover Mode VDO bits */
>  #define TBT_MODE			BIT(0)
>  #define TBT_ADAPTER(_vdo_)		FIELD_GET(BIT(16), _vdo_)
> -#define   TBT_ADAPTER_LEGACY		0
> -#define   TBT_ADAPTER_TBT3		1
> +#define   TBT_ADAPTER_TBT3		0
> +#define   TBT_ADAPTER_LEGACY		1
>  #define TBT_INTEL_SPECIFIC_B0		BIT(26)
>  #define TBT_VENDOR_SPECIFIC_B0		BIT(30)
>  #define TBT_VENDOR_SPECIFIC_B1		BIT(31)
> 
> ---
> base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb
> change-id: 20250926-topic-tbt_header_bit_fix-17aeb524df4a
> 
> Best regards,
> -- 
> Konrad Dybcio <konrad.dybcio@....qualcomm.com>

-- 
heikki